A charging device is generally designed to accommodate several to dozens of digital devices and charge the digital devices. However, charging dozens of digital devices at the same time may cause a power distribution system overload to start the overload protection mechanism, thus resulting in power interruption and causing user disturbance. Therefore, a number of charging areas are provided to ensure that one single charging area supply power source will not cause the power distribution system to be overloaded. Whether the charging area is enabled or disabled to supply power is controlled by the controller collaborating with the power switch. In order to make the charging devices within the charging areas completely charged, the controller keeps switching the power switches based on the charging mechanism. When the power switches are turned on, AC power is supplied to several power supplies at the same time through the power switches, and is converted to DC power to supply power to several digital devices.
In order to stabilize the input power source, input terminals of the power supply are all equipped with large-capacity capacitors, the capacitor will be charged instantly when the power switch is turned on. This instantaneous charging current is inrush current. If the inrush current is too large, a metal contact of the power switch will be melted, and at this point the distribution system will be overload protected and powered off.
The magnitude of the inrush current is related to the phase of the AC voltage corresponding to the moment when the power switch is turned on. If the phase of the AC voltage corresponding to the instantaneous moment when the power switch can be effectively controlled and is turned on, the inrush current of the power switch can be greatly reduced, and the service life of the power switch may be prolonged. In addition, due to the power switch structure design, when the power switch receives the control signal, the contact will not be immediately conducted. Due to the working time of the power switch, time difference may be caused. The time difference may also vary with the aging of the parts caused by the number of switching times.
Therefore, how to ensure that the conduction state always occurs in the time interval in which the smaller inrush current occurs, and how to adjust the working time of the power switch when the power switch varies due to aging or other factors, are the problems needed to be addressed in the art.